1. Field of the Invention
This invention pertains to the telecommunications industry. More particularly, this invention pertains to a high-density fiber distribution frame for use in the telecommunications industry.
2. Description of the Prior Art
In the telecommunications industry, use of fiber optic cables for carrying transmission signals is rapidly growing. To interconnect fiber optic equipment, fiber distribution frames have been developed. An example of a prior art fiber distribution frame is shown in commonly assigned U.S. Pat. No. 4,995,688.
The fiber distribution frame of U.S. Pat. No. 4,995,688 includes a so-called connector module (item 16 in the '688 patent) having a front panel which carries a plurality of adapters (102). Each of the adapters (102) permits attachment of a fiber optic connector (100) to both sides of the adapter in order to optically connect two fiber optic cables.
Typically, the back side of the adapters (102) are provided with connectors secured to fiber optic cables. The cables are connected to various pieces of fiber optic equipment (such as, a fiber-to-copper convertor for converting DS-3 signals to optical signals).
The connections on the back side of the adapters are semi-permanent. Namely, while the connectors on the back side of the adapters can be easily removed, they are normally installed with the intent to maintain the connection of the connector to the rear side of the adaptor without frequent future changes to the connection. On the front side of the adaptor, the fiber optic connector is secured to a fiber cable (for example, a jumper cable) for cross-connecting to other pieces of optical equipment or to any other destination.
With the increase in use of fiber optic cables in the telecommunications industry, it is desirable to provide fiber distribution frames with increased density. By density, it is meant the number of locations per unit volume or unit area for providing connection on the fiber distribution frame.
In products made according to the aforementioned U.S. Pat. No. 4,995,688, a typical fiber distribution frame will have about 576 fiber optic connector locations. In the industry, it is becoming desirable to substantially increase the density to be in excess of 1,400 connectors per frame.
Examples of high-density fiber distribution frames include a frame marketed under the trademark of Fiber Manager by Northern Telecom and described in Northern Telecom Bulletin No. 91-004, Issue No. 2, May, 1991. Another example includes the High Density Interconnect System (HDIC) of AT&T as disclosed in its Product Bulletin 2987D-DLH-7/89, Issue 2.
One problem associated with prior art high-density fiber distribution frames is that the prior art products require substantial displacement of fibers when access to the fiber connectors is required. For example, the Northern Telecom product houses the fibers and connectors in a molded plastic cassette. The cassette is shown on page 7 of the aforementioned Northern Telecom publication. The particular cassette shown has twelve connectors (paired into six connections). To access any one of the twelve connectors, the cassette must be pulled from the frame approximately three to four inches at which point the cassette drops to an access position as shown on page 6 of the aforementioned bulletin. As a result, even though only one connector may require access, a total of twelve connectors are displaced with substantial displacement of the fiber optic cables associated with each of the twelve connectors.
Unnecessary or excessive displacement of fiber optic cables is undesirable. As fiber optic cables are displaced, they are subject to bending and other forces. As a fiber bends, the fiber can break resulting in loss of transmission through the fiber. Since fibers carry extremely high signal rates, the breakage of a single fiber can result in a substantial loss of data or voice communications. Telecommunications industry standards generally recognize a minimum bending radius of about one and a half inches for optical fibers.
It is an object of the present invention to provide a fiber distribution frame which permits high density, ready access to fiber optic connectors and minimal displacement of fibers when access is being made to connectors.